The FCC is holding its first C-band auction since 5G became more established in the US, which T-Mobile, Verizon, and AT&T are closely monitoring.

AT&T and Verizon may have initially underestimated the limitations of mmWave signals, which have a short range. Low-band signals offer the greatest range, making them suitable for nationwide networks, but they have the slowest speeds. T-Mobile chose mid-band, acquiring Sprint for $26 billion to gain access to it.

Mid-band spectrum at 2.5GHz offers a balance between range and speed, surpassing low-band in speed but not reaching the speed of mmWave. Recognizing their earlier focus, AT&T and Verizon participated in FCC auction 107 on February 17, 2021, to obtain mid-band spectrum.

The auction generated over $81 billion in winning bids, a record that remains today. Verizon acquired 3,500 licenses for over $45 billion, while AT&T spent over $23 billion for 1,600 licenses. T-Mobile spent more than $9 billion for 162 licenses. In the U.S., the C-band spans 3.7 to 3.98GHz. Initially, concerns about interference with aircraft radio altimeters restricted Verizon and AT&T from using spectrum near airports. In 2023, the FAA and the carriers reached an agreement regarding C-band use near airports.

This leads to the first C-band auction in years. The FCC recently approved a Notice of Proposed Rulemaking (NPRM) outlining options for auctioning 100MHz to 180MHz of upper C-band spectrum. Congress has mandated that these airwaves be auctioned off by July 4, 2027. The NPRM includes options that would allow 5G/6G signals to coexist with radio altimeters.

The FCC's NPRM passage starts a 30-day period for public comments, followed by another 30-day period for reply comments. Currently, the FCC and other stakeholders appear on track to meet the July 2027 deadline. Verizon and AT&T are expected to actively bid to expand their mid-band spectrum holdings in the C-band.

Verizon and AT&T are likely to be the primary bidders in the auction. Similar to the 2021 auction, T-Mobile might also acquire some C-band airwaves, continuing to expand its 2.5GHz holdings.

The FCC has been in discussions with the National Telecommunications and Information Administration (NTIA) and the wireless and aviation sectors. FCC Chairman Brendan Carr stated that there has been strong collaboration with all stakeholders.

Elon Musk's SpaceX/Starlink had pressured the FCC to release more upper C-band for alternatives to terrestrial connectivity. However, SpaceX's $17 billion agreement to acquire 2 GHz and AWS-3 spectrum from EchoStar has reduced the urgency of its participation in the auction, though SpaceX/Starlink may still be present during the bidding.